Crank scraper... Check this out!

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=46098&item=2427431739

Any thoughts, opinions, etc.?

Thats an interesting Idea. I don't think it would build a large amount of power but it does reduce the rotating mass of the crank by scraping the oil off of it, and that does mean a HP gain. For a rock crawler, it could alow operation at steeper angles because it forces oil into the sump.

I like it but usually they are held by the bearing cap bolts, so I would be a tiny bit concerned about the added clearance between the oil pump pick up and bottom of the oil pan..course you could just add some more oil to make up for it and then your dip stick will read correct again as well.

XJguy

Drag racers have been doing that for years. I believe most of your gains will be at higher RPM's. Plus they can be a pain in the ass to fit, they never seem to clear each crank just right.

I've seen that crank scraper before on e-bay. It's a nice idea and I'm sure it works but since the HP losses from windage are proportional to the square of the rpm, it's only at higher rpm that you'll notice any difference. I'd like to see some dyno tests to find out how much of a HP gain it produces. For $50, I guess even just a 3hp gain would be worth it, and perhaps a small gain in mpg too.

You mean no company has ever made a crank scraper for the 4.0 engine? That's odd.

It make sense that the scraper works best at high RPM, something the 4.0 is not know for. I wonder how many hp it saves at say 3K.

My guess is that you wouldn't even be able to measure the difference until you got up into the 5k range.

Oil Return?

Somebody smarter than me pointed out that the oil returns on the cam side of the 4.0; unlike the V8's and that scraper would collect all the oil on top of it before allowing it to get back by the crank to the pan!

Oooo, that's bad. Forget I asked.

Re: Oil Return?

rsalemi said:

Somebody smarter than me pointed out that the oil returns on the cam side of the 4.0; unlike the V8's and that scraper would collect all the oil on top of it before allowing it to get back by the crank to the pan!

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Yes, the actual scraper has drain holes in it. I guess no-one ever thought of doing that before.

Kevin

Dr. Dyno said:

I've seen that crank scraper before on e-bay. It's a nice idea and I'm sure it works but since the HP losses from windage are proportional to the square of the rpm, it's only at higher rpm that you'll notice any difference. I'd like to see some dyno tests to find out how much of a HP gain it produces. For $50, I guess even just a 3hp gain would be worth it, and perhaps a small gain in mpg too.

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Yes, for normal windage losses that is true -- the oil gets drawn into a cloud around the crank at higher rpm. On the little 2.2 engines Chrysler and Mobil regained 7hp at 6000rpm (9hp with Mobil-1). The design of the 4.0 is similar and the windage losses would be magnified.

For off-road vehicles (or road-racers), however, low rpm losses can be significant too because of engine angles. Smokey Yunick is one of the few engine tuners that I know of that tilted his engines on the dyno to get realistic effects due to oil sloshing or g-forces.

In my Grand Wagoneer I run a 360 and the effect is noticible -- worth noting on a 6000lb vehicle. One customer bought and installed one on his Grand Wagoneer with a 258/4.2 straight six and said the difference was noticible. I would suggest installing it on a removed engine, though.

Kevin

The link has changed so here's the new one:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7915176584&category=46098

Here's a pic of the 4.0 crank scraper:



The 4.0 crank has 8 counterweights so if you have a stroker, you'll need a scraper for either a 4-counterweight crank or for a 12-counterweight unit. Since they're not readily available, you'd need to have one made.
The '96+ 4.0's have a main bearing stud girdle, so I wonder if the scraper causes any interference problems?

Dr. Dyno said:

The '96+ 4.0's have a main bearing stud girdle, so I wonder if the scraper causes any interference problems?

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A local engine recycler lets me borrow cores -- I think I saw examples of the 4.0 you are talking about. If it is the one with a a steel bridge connector running along the main caps then, no, it will not interfere. The scraper sits at the plane defined by the oil pan rail. Some designs I have made for other engines do run along the main bearing caps.

Kevin

dmillion said:

My guess is that you wouldn't even be able to measure the difference until you got up into the 5k range.

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We did dyno pulls with the little three-cylinder 993cc SOHC Metro engine -- the horsepower increased from roughly 2750rpm through 5300rpm. Despite having a stock full windage tray an average 3% hp was regained (at 5300rpm). Four pulls gave data ranging from 2.5% to 3.5%. The Metro three cylinder is interesting for an offroad group because it really has a lot of torque low in its rpm range. We use that poor thing to haul sheet steel and engine blocks around.

A Honda racing team got back to us yesterday -- the D16 scraper regained between 1.5% and 3% depending on rpm. That engine has a fairly massive girdle structure running along the mains and many people thought that there would not be significant gains with a scraper.

dmillion said:

My guess is that you wouldn't even be able to measure the difference until you got up into the 5k range.

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It seems that you are right. Take a look at the dyno curves comparing the HP/TQ outputs with and without the scraper on the aforementioned Geo Metro engine:

http://www.crank-scrapers.com/dyno.html

There seems to be a very small torque gain with the scraper from 2750rpm and up but it's only from 5000rpm and up that the gain becomes significant. At 5300rpm, there's a 2.4% gain if we compare the HP with scraper with the best HP number without the scraper. That makes sense since the windage TQ losses increase dramatically at higher rpm and that's where you'd expect the scraper to produce the greatest benefit.
Like Kevin said, I'm sure that there would have been higher measureable HP/TQ gains if the Metro engine didn't have a windage tray from the factory. Since the Jeep engines fit into that category, the scraper should work better on these.

I strongly suspect higher numbers would result in the same engine with the windage tray removed (I might yet test this).

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A dyno test on the same Metro engine with the windage tray removed from the oil pan would be a very good idea. It'll give us a better idea of how the scraper will perform in the Jeep engine.

Kevin, I was that customer who posted eBay feedback regarding a noticeable high-rpm difference. I also want your potential customers to know that, while I'm overall happy with the project, it was a major league PITA to install this item.

I spent 13 hours on the project. The fitment process was agonizing, installing and removing the crank scraper to trim it for clearance around the crankshaft and oil pump. And after all my work I still ended up with the crankshaft knocking against the scraper; after 10k miles the noise has lessened considerably but is still present.

The quality of your crank scraper is first-rate in terms of the precision cutting; however, as I pointed out to you in our emails, I did't trust using only RTV silicon as a gasket. It wouldn't hurt for you to conjure up a gasket set to work with your product. I've got some seepage around the rear main seal that just irks me.

In the near future I'll be dropping the oil pan again, along with the front timing cover, so that I can tap the oil pan or a turbocharger drain and install a double-roller timing chain. I plan to experiment with gaskets and will post here my results.

Hate to quibble but it is wrong even at the lower rpms. (I guess we could talk about p values and so forth in statistical analysis.) The gain is significant experimentally and practically for having done nothing else to the engine but remove one part (the scraper). I tried to be very careful with the pulls. I drained and reused the same oil -- left the same filter in place. I had put the oil in fresh the night before (10w-40 dino oil) so it had less than 100 miles on it. The swap on the dyno lift took about 30 minutes so the weather was as close as you could get to being the same.

The dyno operator seemed a bit surprised by the results.* The first pull after removing the scraper gave a 3.19% increase. He then put a portable blower in front of and just under the car to cool the engine for quite a while. He ran the remaining three pulls with the cooling fan on as well. Yes, one of those values was 2.4% but one of the highest values also resulted, i.e. 3.5%.

It is worth noting that the Honda team reported similar data though they made it clear from the beginning that they would not release dyno charts for their race engines. Take a look at the girdle structure on the D16 series engines.

*I'll be honest as to why -- I had done a previous set of pulls a couple weeks prior with the scraper on reversed (opposite side of the motor) so that the removed oil could not directly drain into the sump. Not sure why I did that! (Laugh!) I guess I got turned around while lying on my back working on a symmetrical engine. That data showed no real statistical difference.

Kind regards,

Kevin Johnson

Dr. Dyno said:

It seems that you are right. Take a look at the dyno curves comparing the HP/TQ outputs with and without the scraper on the aforementioned Geo Metro engine:

http://www.crank-scrapers.com/dyno.html

There seems to be a very small torque gain with the scraper from 2750rpm and up but it's only from 5000rpm and up that the gain becomes significant. At 5300rpm, there's a 2.4% gain if we compare the HP with scraper with the best HP number without the scraper. That makes sense since the windage TQ losses increase dramatically at higher rpm and that's where you'd expect the scraper to produce the greatest benefit.
Like Kevin said, I'm sure that there would have been higher measureable HP/TQ gains if the Metro engine didn't have a windage tray from the factory. Since the Jeep engines fit into that category, the scraper should work better on these.



A dyno test on the same Metro engine with the windage tray removed from the oil pan would be a very good idea. It'll give us a better idea of how the scraper will perform in the Jeep engine.

Click to expand...

Hi Ralph,

Yes, I remember! I quote you on the opening page of the website too because I don't want people to have unrealistic expectations.

A few things should be said though with respect to your installation.

First of all, readers should understand that I also have an 86 Grand Wagoneer so I am familiar with Ralph's ride.

When I installed the scraper on the 360 it was removed from the vehicle and on a stand but your straight six was not. I suspect most people with a longitudinally mounted engine with rear drive would install the scraper off the vehicle. My installation took about 1.5 hours and included taking pictures and waiting for rtv to set up.

I guess if I included the time to pull and replace the engine it might be up around 13 hours though you mentioned you had a fully equipped shop which I don't have.

I run full synthetic 5W-50 oil in the GW and have no leaks. RTV picked up a really bad rap dating back to the 70s (maybe earlier -- I personally remember the issues in the 70s). That is history now -- I have a couple engineering abstracts that relate OEM evaluations/testing of modern RTV silicone gasket products. It is really critical to have a clean surface when using RTV or otherwise you are simply building in a leak.

For what it's worth, the installation of the Metro scraper took 2-3 hours on jackstands in my driveway. Most of that time was spent in frequent breaks and waiting for rtv to set up.

Kind regards,

Kevin Johnson

FSJ Ralph said:

Kevin, I was that customer who posted eBay feedback regarding a noticeable high-rpm difference. I also want your potential customers to know that, while I'm overall happy with the project, it was a major league PITA to install this item.

I spent 13 hours on the project. The fitment process was agonizing, installing and removing the crank scraper to trim it for clearance around the crankshaft and oil pump. And after all my work I still ended up with the crankshaft knocking against the scraper; after 10k miles the noise has lessened considerably but is still present.

The quality of your crank scraper is first-rate in terms of the precision cutting; however, as I pointed out to you in our emails, I did't trust using only RTV silicon as a gasket. It wouldn't hurt for you to conjure up a gasket set to work with your product. I've got some seepage around the rear main seal that just irks me.

In the near future I'll be dropping the oil pan again, along with the front timing cover, so that I can tap the oil pan or a turbocharger drain and install a double-roller timing chain. I plan to experiment with gaskets and will post here my results.

Click to expand...

I hope the tone of my reply wasn't too harsh, Kevin, because at the end of the day I really liked what your product did for my ride.

And your thorough answers are exemplary of the kind of attention I received from you before, during and after I purchased and installed the crank scraper.

Just want others on this forum to benefit from my experience.

(And I really liked the cool refrigerator magnet you sent me!)

Kevin Johnson said:

Hate to quibble but it is wrong even at the lower rpms. (I guess we could talk about p values and so forth in statistical analysis.) The gain is significant experimentally and practically for having done nothing else to the engine but remove one part (the scraper). I tried to be very careful with the pulls.

Click to expand...

It certainly does look like you took every precaution to ensure that the results were valid and the attention to detail is there for all to see.
I had difficulty reading the dyno curves mainly because at lower rpm, there were five plots overlapping one another. Perhaps if you could average the first four plots done without the scraper into one plot and add the plot done with the scraper, it'll be much clearer.
At higher rpm, the difference the scraper makes is readily apparent. At 5000rpm, there's a potential 6-7hp gain on a 260hp stroker so for just $50, it's definitely a worthwhile mod.
I can't wait to get mine on. I hope the installation won't be a PITA like Ralph's. I might try to conjure up my own oil pan gasket so I don't have any leakage problems later on.